Nested can brush seal

ABSTRACT

A method of forming a brush seal which includes placing a bristle hoop sandwiched by a sideplate and a backplate in the cavity of a forming die. The components are then die formed together into a unitized brush seal.

FIELD OF THE INVENTION

This invention relates generally to a brush seal and more specificallyto a method of making a lower cost and/or lighter weight brush seal.

BACKGROUND OF THE INVENTION

Brush seals are commonly used on gas turbine engines. The brush seal istypically used to prevent secondary flow in the engine from escapingthrough a gap between a stationary part such as a diffuser case and arotating part (e.g. a turbine shaft). Brush seals may also have otheruses, such as sealing a gap between stationary parts of the engine.

A brush seal typically includes packs of wire bristles sandwichedbetween plates. The bristle packs and plates are typically weldedtogether to form the brush seal. The brush seal must undergo heattreatment after the welding step to relieve any residual stresses. Heattreatment typically involves securing the brush seal within a fixture,then placing the fixture in an oven. The heat treatment process is timeconsuming and can be expensive.

The welding step transforms the discrete sub-assemblies of the brushseal into one piece. The one-piece arrangement prevents the removal of asub-assembly without affecting or damaging the remainder of the brushseal. This means a mechanic must replace the entire brush seal duringmaintenance. Replacement of the entire brush seal must occur despite thefact that only one of the sub-assemblies (typically the bristle packs)needs replacement.

The bristle packs of the brush seal are expensive. The main factorinfluencing cost is the amount of raw material used. Each individualbristle in the bristle pack is a taken from a length of wire. A commonlyused wire is a 0.0028″, 0.004″ or 0.006″ diameter cobalt alloy wire. Onetype of bristle pack can have approximately 5000 bristles per linearinch. This type of bristle pack clearly contains a large amount of wire.When used in a 12″ outer diameter single stage brush seal, this type ofbristle pack can contain approximately 2.6 miles of wire.

It is therefore an object of the present invention to provide a new andimproved brush seal.

It is a further object of the present invention to provide a method ofproducing a lower cost and/or lighter weight brush seal.

It is a further object of the present invention to produce a brush sealthat requires less machining and/or welding.

It is a further object of the present invention to produce a brush sealat a reduced cost.

It is a further object of the present invention to produce a brush sealthat uses less raw material.

It is a further object of the present invention to provide a brush sealthat may not require heat treatment.

SUMMARY OF THE INVENTION

The invention relates to a method for producing a low cost, lightweightbrush seal by mechanically forming and joining the components togetherin a die.

The brush seal of the present invention utilizes formed sheet metal sideand backplates. The cross sectional shape of the plates approximates an“L”. One plate is placed in a die and a bristle hoop then placed insidethe first formed sheet metal. A plunger is then employed to force asecond formed sheet metal plate inside the first sheet metal component,capturing the bristle hoop between the two. The plunger sizes both sheetmetal elements during the process. Optionally, spot welding afterforming can be used to ensure that the components remain securelyattached.

The resulting formed sheet metal configuration would allow platethickness to be reduced and still maintain similar structural integrityto machined plates. With only spot welding optionally used to secure thetwo sheets, a final seal stress relieve step may not be needed. Thismethod allows for all features and details to be formed and die cut intothe two “plates” to eliminate the need to machine the details.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further understanding of these and objects of the invention,reference will be made to the following detailed description of theinvention which is to be read in connection with the accompanyingdrawings, where:

FIG. 1 is a side sectional view of one embodiment of the sizing die andseal components in place prior to a die forming step.

FIG. 2 is a view of FIG. 1 following action by a forming plunger.

FIG. 3 is a sectional view through one embodiment of a finished brushseal of the invention.

FIG. 4 is a perspective view of a bristle hoop.

FIG. 5 is a side view of bristle tufts illustrating typical bristleorientation.

FIG. 6 is a perspective sectional view of one embodiment of a brush sealof the invention in use.

FIG. 7 is a perspective sectional view of the brush seal of theinvention mounted in a support housing using a retaining ring.

FIG. 8 is a perspective sectional view of the brush seal of theinvention mounted in a support housing using screw means.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic illustration of one embodiment of a formingstation for a brush seal which consists of a sizing die 10 which definesa die cavity 12 having a substantially flat bottom 14 and side walls 16.A forming plunger 18 is positioned above the die cavity and is adaptedfor vertical downward and upward movement as indicated by the verticalarrows in the drawings.

In operation, a backplate ring 20 is placed in the bottom of die cavity12. The backplate ring can have a cross-sectional shape in the form ofan “L”. Ring 20 can be circular in geometry and can have a centralopening 22. In addition to an annular ring, segments of an annular ringor a linear bristle arrangement can also be used. In one embodiment, abristle hoop 24 is then placed inside (in a radial sense) the backplatering 20 as shown in FIG. 1. The bristle hoop 24 consists of a weld joint26 which holds a plurality of bristles in place in the form of a bristlepack 28 such as that described in United States Patent ApplicationPublication Number 2003/0178778A1, herein incorporated by reference. Asideplate ring 30 can have a complementary “L” shape configuration andcentral opening 32. It should be understood that other configurationsother than an “L” cross-section can be used. For example a cross-sectionapproximating a “C” or a crescent may also be used. As seen in FIG. 1,the side plate 30 has an outer diameter larger than the inner diameterof the flange 21 of the back plate 20. After placing the side plate 30against the bristle hoop 24, the plunger 18 is then activated, forcingsideplate ring 30 inside backplate ring 20, and capturing bristle hoop24 between the two rings. The angled arrows in FIG. 1 illustrate thethrust of the forming forces which force sideplate ring 30 insidebackplate ring 20. The plunger 18 sizes both rings during the formingprocess as shown in FIG. 2 with the forming resulting in a brush sealhaving the rings and bristle hoop being held together mechanically infixed engagement. Typically plates 20 and 30 are made of a corrosionresistant alloy such as stainless steel or Inconel.

In an alternative embodiment, the orientation of the leg of the “L”shaped cross section may be reversed relative to the position of thesideplate and backplate. This alternative embodiment allows for suitablemounting of the seal into supporting housings (not shown) and toaccommodate for variation in the direction of fluid flow across theseal.

In another embodiment, the rings and bristle arrangement may be joinedtogether by a thermal press fit. In this embodiment the inner platewould be chilled to a temperature below room temperature, and the outerplate (with bristle hoop) would be heated to a temperature above roomtemperature. Once the components are stabilized at these temperatures,the plates, with the hoop captured inside, can be assembled. The plateinterface (ID Of inner plate, OD of outer plate) would be sized for aninterference fit when the temperature of the joined assembly componentsis equalized (i.e. brought back to room temperature). The chilling andheating temperatures chosen would be dependent on the relative size ofthe seal, and the thermal coefficient of expansion of the metal(s)chosen for the plates. A jig or fixture may be used to align the twoplates for proper assembly.

FIG. 3 illustrates a cross sectional view through one embodiment of afinished seal 32. The formed brush seal may be spot welded at 34 toensure that the components remain permanently attached. Other methods ofattachment include crimping the “L” section of plates, brazing, drillingand subsequently bolting or riveting the plates together.

FIG. 4 is a view of a typical bristle hoop 24 having bristle packs 28held in place by a weld joint 26. FIG. 5 is a side view of bristle tufts40 illustrating typical bristle orientation.

In FIG. 5 the jagged bristle ends represent an unfinished bristle endsurface which is finished before use to form a final smooth contactsurface using conventional techniques.

In FIG. 6 illustrates the finished brush seal of FIG. 3 in place againsta rotatable shaft 42.

FIG. 7 illustrates the brush seal of the invention mounted in a supporthousing 44. The brush seal is maintained in place by a split retainingring 48 which is held in place through locking flange 50 contained inslot 46 of the housing.

FIG. 8 illustrates an alternative embodiment for mounting the brush sealin which a plurality of cap screws 52 are used to attach the brush sealto support housing 44 through a hole(s) 54 through the leg of the brushseal.

While the present invention has been particularly shown and describedwith reference to the preferred mode as illustrated in the drawing, itwill be understood by one skilled in the art that various changes indetail may be effected therein without departing from the spirit andscope of the invention as defined by the claims.

1-11. (canceled)
 12. A unitized brush seal made by the method which comprises; (a) providing a sizing die which includes a molding cavity having a substantially flat bottom section, and an associated forming plunger, (b) positioning a backplate ring component in the bottom section of said molding cavity; (c) placing a bristle hoop component in engagement with and inside of said backplate ring component; (d) placing a sideplate ring component over said bristle hoop and inside of said backplate ring component thereby capturing said bristle hoop component between said two ring components, and (e) activating said plunger to force and join said components together in fixed engagement to form of a unitized brush seal.
 13. The seal of claim 12 in which both ring components have a cross sectional shape which approximates an “L” and define a bottom and side wall, respectively.
 14. The method of claim 13 in which the side walls of the finished brush seal are spot welded at selected locations.
 15. A die formed brush seal which includes a backplate ring and a sideplate ring which flank and secure a bristle arrangement which comprises; (a) a backplate ring having a “L” shaped cross section; (b) a sideplate ring contained and nested inside and in fixed engagement with said backplate ring and having a “L” shaped cross section; and (c) a bristle hoop captured and secured between said two rings, with said rings and hoop being mechanically held together in fixed engagement to form a unitized brush seal.
 16. The brush seal of claim 15 in which the seal has a “L” shaped cross section and contains a central opening with the bristles being in an annular arrangement within said opening.
 17. The seal of claim 16 which contains a plurality of spot welds which aid in holding said two rings together. 